The standard fuel system for a diesel engine includes, in connected series, a tank adapted to contain liquid diesel fuel therein, a transfer pump, injection pumps and a plurality of injectors for injecting diesel fuel into the combustion chambers of the engine. When the fuel in the tank of a vehicle is low and the vehicle stops abruptly, starts or sharply changes its attitude, air will tend to enter the fuel line to the injection pumps to induce engine stalling. It is common practice to install a sock-like steel mesh strainer at the outlet from the fuel tank to aid in counteracting the air vortexing and cavitation effect that induces engine stalling.
However, use of this type of strainer is not totally efficient and will not prevent air from entering the fuel line when the fuel tank becomes empty and also when the engine is restarted after refilling of the tank. In either situation, stalling of the engine normally requires towing of the vehicle to a service facility for the purpose of removing air from the fuel lines to enable the engine to be restarted. Further, strainers of this type periodically become clogged and require removal of the fuel tank for cleaning and replacement purposes. This procedure is unduly expensive and involves substantial "downtime."
Various devices have been proposed for the purpose of preventing the communication of air through the fuel line and to the fuel pumps of an engine when the fuel in the tank drops below a predetermined low level. For example, U.S. Pat. No. 4,602,605 discloses an automatic shut-off device for the fuel system for a diesel engine wherein a float switch is actuated to shut an engine down in response to the fuel dropping below such a low level in the fuel tank. The device has a bleed orifice that allows trapped air to escape and return to the fuel tank when the tank is refilled with fuel. Various other systems have been used in fuel systems of this type to purge air therefrom.
Conventional systems of this type are generally complex in construction and do not insure the reliability required. For example, adequate fuel is not provided, after the driver has been alerted that a "low fuel" or clogged fuel filter condition of engine operation exists, to permit the driver to safely drive off a roadway. Further, no provision is made for restarting the engine expeditiously.